What describes materials that do not allow electricity to flow through them?

Materials that do not allow electricity to flow through them are known as insulators. Insulators have tightly bound electrons that do not move freely, making it difficult for electrical currents to pass through. Common examples of insulators include rubber, glass, and most plastics, which are often used to protect electrical wires and components from unintentional contact with conductive materials.

In contrast, conductors are materials that allow electricity to flow readily, typically due to the presence of free electrons. Metals like copper and aluminum are prime examples of conductors. Semiconductors, on the other hand, exhibit properties between those of conductors and insulators and can conduct electricity under certain conditions, such as when they are doped with impurities or subjected to specific temperatures. Resistors are components that limit the flow of electric current, but they do not inherently prevent the flow of electricity like insulators do; instead, they provide resistance to it.

Thus, the defining characteristic of insulators is their inability to allow electricity to flow, making them essential in various electrical applications where preventing current flow is necessary.